Method of manufacturing barrier ribs for pdp by etching of thick film using water-based solution and compositions therefor

ABSTRACT

Disclosed is a method of manufacturing barrier ribs for a Plasma Display Panel (PDP), which includes the steps of forming a thick film (or, “green tape”) for barrier ribs on a glass or metal substrate by using composition for forming the barrier ribs, which contains water soluble components and solvent soluble components together a binder; forming a protective pattern film partially soluble or insoluble to the water based solution on the thick film; etching the thick film into a barrier rib shape by using solution or mixed solution containing ceramic powder as an etching accelerator, and sintering the etched thick film. This method causes rare environmental pollution, enables to make barrier ribs having fine and complex shapes and reduces material costs required for the barrier rib. Thus, the method may improve quality of DPD and reduce manufacture costs of the rear plate.

TECHNICAL FIELD

The present invention relates to a method of manufacturing barrier ribsfor a rear plate of a Plasma Display Panel (PDP) by etching in anunfired state using water-based solution and composition used for themethod, and more particularly to a method of manufacturing barrier ribsby forming a thick film for barrier ribs using composition containing abinder composed of water soluble components and solvent solublecomponents and then etching the thick film using water-based solution.

BACKGROUND ART

A Plasma Display Panal (PDP) is a flat display panel, which is mainlyused for large-sized display devices over 40 inches because the PDP isthin and light and offers good images quality. In the PDP, pixels areformed at the position where barrier ribs and address electrodes formedon a rear plate intersect sustain electrodes formed on a front plate todisplay an image. The PDP is schematically shown in FIG. 1. Referring toFIG. 1, a dielectric layer 9 is coated on a rear plate 8 made of a glassor metal substrate, and address electrodes 5 are formed on the lowerplate 5 or the dielectric layer 9. Barrier ribs 6 having a long stripeshape are positioned between the address electrodes 5, and fluorescentmaterial is coated on the surface between the barrier ribs 6 in order tocompose a sub-pixel. A sustain electrode 4 is embedded in a front plate1 made of glass, and a dielectreic layer 2 and an MgO protective layer 3are provided below the sustain electrode 4. Thus, when the front plate 1is combined with the rear plate 9, there generates a plurality of pixelspaces separated by the barrier ribs 6. These separated spaces arefilled with He/Xe gas or Ne/Xe gas so as to create plasma therein whenvoltage is applied to the sustain electrode 4 and the address electrode5. Subsequently, vacuum ultra violet generated from the plasma excitesthe fluorescent material coated on the side walls of the barrier ribsand bottom surfaces between the barrier ribs, thereby creating red,green and blue visible light.

In order to form the barrier ribs, the sand blasting is mainly used.FIG. 2 schematically shows sequential processes of the sand blasting. Asproposed in Japanese Patent serial No. 11-120905 and Korean Patentapplication No. 2000-10322 in detail, the sand blasting is executedaccording to the following procedure: coating paste containing glasspowder for barrier rib and a ceramic filler on a rear plate such as aglass board and then drying, which is repeated several times until tohave a thickness of about 200 μm, coating photoresist on the dried thickfilm; and developing the film except portions corresponding to thebarrier ribs to be removed. At this time, the exposed portion isdetermined depending on the type of the photoresist film. And then,ceramic powder such as calcium carbonate (CaCO₃) is sprayed togetherwith high pressed air onto the film coated with photoresist in order toetch the portions where the photoresist is removed, thereby forming thebarriers ribs.

The sand blasting is relatively stable and thus frequently used to makethe barrier ribs of the existing PDP. However, the sand blasting hasdrawbacks in that complicated processes are required to manufacture thebarrier ribs, the side walls of the manufactured barrier ribs are notuniform, and the drying and coating process is executed very slowly.

Recently, as the picture definition of the PDP improves, the pitch ofthe sub-pixel between the barrier ribs is decreased from 420 μm to 200μm, which needs a method for making a barrier rib having a thicknessless than 50 μm. In case the pitch of the sub-pixel is 200 μm and thethickness of the barrier rib is 50 μm, the open ratio becomes 50%, whilein case the cell pitch is 100 μm, the open ratio becomes 0%, and therebyit is impossible to compose the display panel. Thus, it is required thatthe barrier rib has a thickness between 20 μm and 30 μm. However, thesand blasting is substantially impossible to obtain such thickness.Since ceramic powder and high-pressure gas are used for etching to formthe barrier ribs, it is hardly possible to make a thin barrier rib sincethe barrier rib is broken due to the mechanical energy of the ceramicpowder and the high-pressure gas. In addition, if the pitch of thesub-pixel is 430 μm and the width of the barrier rib is 50 μm during themanufacture of the barrier ribs using the sand blasting, at maximum 90%of the volume of the thick film is etched and removed. Thus, the sandblasting generates a large amount of wastes. Furthermore, glass frit ofthe thick film containing a large amount of lead monoxide may causeenvironmental pollution.

As another example, a method for forming barrier ribs by etching thefired glass {SID 01 Digest, p537(2001)}. This method is now brieflydescribed. At first, a thick film having a predetermined thickness isformed on a glass substrate by using the paste including glass powderand ceramic powder. The thick film may be formed by using the well-knownprinting and drying process repeatedly, or by lamination using a dryfilm. After the thick film is formed, the thick film is heated up to apredetermined temperature with a predetermined temperature profile, andthen to make a thick film. A photosensitive film is coated or laminatedon the surface of the fired thick film, and then the photosensitive filmis selectively exposed to light with a mask. The exposed specimen isdeveloped to form an etching protective pattern film of thephotosensitive film, and then the exposed thick film is etched bysuitable etchant. And then, through washing and drying processes,barrier ribs for PDP are finally manufactured. This method mayadvantageously make a barrier rib having fine and complex shape since itdoes not require the etching process using mechanical impacts. However,the dense glass thick film is generally slowly etched, particularlyexperiencing the isotropic-etching. Thus, Photonics Co. provides amethod for improving a barrier rib forming speed by etching a porousthick film {SID 01 Digest, p532(2001)}.

Such a etching method has some problems as follows. First, since thefires barrier rib material layer is etched by an etching solution suchas acid, environmental pollution may be caused by wasted water. Sincethe layer to be etched is thick as much as 120 μm˜150 μm, an amount ofthe wasted water is very significant, thereby requiring much costs fortreating the wasted water. Second, physical features required for thebarrier rib material such as electric resistance, dielectric constant,thermal expansion coefficient and reflectivity should be satisfied, andthe material should be rapidly etched by the water-based solution. Thus,there are many limitations in selecting the material, and thus theselection of the barrier rib material is very limited. Finally, whenapplied to a large area, this etching method may hardly obtain a uniformetching speed. In other words, in order to have a uniform etching speedthroughout the large area and give a desired shape for the barrier ribof the PDP, the etching conditions should be maintained very accurately.However, to maintain the conditions throughout the large area is veryhard, thereby resulting in very low process yield.

DISCLOSURE OF INVENTION

The present invention is designed to solve problems of the prior art byone effort and achieving technical objects desired up to now, asdescribed below.

Firstly, the present invention is directed to prevent dust generationcaused by the sand blasting in addition to mechanical damage of barrierribs by etching the thick film for forming the barrier ribs with the useof water-based solution.

Second, the present invention is directed prevent environmentalpollution, which may be generated during forming the barrier rib, byproviding a pollution-free mechanical-chemical etching.

Third, the present invention is directed to provide a process ofmanufacturing barrier ribs, which may be applied to the products such asHDTV requiring the fine pitch barrier ribs.

Fourth, the present invention is directed to improve productivity andquality in manufacturing a thick film for barrier ribs in case offorming the thick film for barrier ribs by laminating a dry film (or, agreen tape) on such as a glass substrate.

In order to accomplish the above objects, the present invention providesa method of manufacturing barrier ribs for a Plasma Display Panel (PDP)comprising the steps of: forming a thick film (or, “green tape”) forbarrier ribs on a glass or metal substrate by using composition forforming the barrier ribs, which contains water soluble components andsolvent soluble components together as a binder; forming a protectivepattern film partially soluble or insoluble to the water based solutionon the thick film; etching the thick film into a barrier rib shape byusing solution or mixed solution containing ceramic powder as an etchingaccelerator; and sintering the etched thick film.

Preferably, the method includes the steps of: (1) making a slurry bymixing glass powder and ceramic powder so that a mixing ratio is in therange between 50:50 and 95:5(volume ratio), and then mixing 20 to 40 wt% of binder including water soluble components and solvent solublecomponents, 3 to 18 wt % of plasticizer and 0.5 to 2 wt % of dispersionagent and defoaming agent on the basis of 100 wt % of the mixed powder;(2) making a thick film by coating the slurry on the glass or metal rearplate in the thickness of 5 to 200 μm, and then drying the coated slurrynaturally or artificially under a predetermined temperature profilecondition; (3) forming the etching protective pattern film partiallysoluble or insoluble to etching solution through printing or exposure,development and printing on the thick film formed on the glass or metalsubstrate; (4) etching the thick film on which the protective patternfilm is formed into a barrier rib shape by water spraying the solutionor the mixed solution in which the ceramic powder is included as etchingaccelerator; and (5) removing the protective pattern film and thensintering the specimen at 450° C. to 600° C. for 0.5 to 1 hour.

According to another aspect of the invention, there is also providedcomposition for manufacturing barrier ribs for a Plasma Display Panel(PDP), which includes (a) 100 wt % of mixture of glass powder andceramic powder of which a volume ratio is in the range of 50:50 to 95:5;(b) 20 to 40 wt % of solvent; (c) 2 to 12 wt % of binder including watersoluble components and solvent soluble components together; (d) 3 to 18wt % of plasticizer; and (e) 0.5 to 2 wt % of dispersion agent and/ordefoaming agent.

According to still another aspect of the invention, there is alsoprovided a Plasma Display Panel (PDP) using the barrier ribsmanufactured according to the above method.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of preferredembodiments of the present invention will be more fully described in thefollowing detailed description, taken accompanying drawings. In thedrawings:

FIG. 1 is a perspective sectional view schematically showing a PlasmaDisplay Panel (PDP);

FIG. 2 is a schematic view for illustrating the process for coating afilm by using a Doctor blade tape casting device;

FIG. 3 is a schematic view for illustrating the process formanufacturing barrier ribs by using the sand blasting;

FIG. 4 is a schematic view for partially illustrating the process formanufacturing barrier ribs according to an embodiment of the presentinvention;

FIG. 5 is a graph showing an etching speed depending on a pressure ofwater-based solution according to the manufacturing method of thepresent invention;

FIG. 6 is a graph showing an etching speed depending on a flow rate anda nozzle size according to the manufacturing method of the presentinvention;

FIG. 7 is a picture photographed by the scanning electron microscope forshowing a section of the barrier rib manufactured according to the firstembodiment; and

FIG. 8 is a picture photographed by the scanning electron microscope forshowing a section of the barrier rib manufactured according to thesecond embodiment.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

A method of manufacturing barrier ribs for a Plasma Display Panel (PDP)according to the present invention includes the steps of: forming athick film (or, “green tape”) for barrier ribs on a glass or metalsubstrate by using composition for forming the barrier ribs, whichcontains water based components and solvent soluble components togetheras a binder; forming a protective pattern film partially soluble orinsoluble to the water soluble solution on the thick film; etching thethick film into a barrier rib shape by using solution or mixed solutioncontaining ceramic powder as an etching accelerator; and sintering theetched thick film.

One of the characteristics of the present invention is that the chemicaletching for dissolving the water soluble components in the thick filminto the solution is executed together with the mechanical etching forremoving the chemically etched thick film by means of mechanical energyof the sprayed solution, thereby making the barrier ribs having a highwidth-length ratio and an excellent etched shape. In other words, themethod for manufacturing barrier ribs for PDP according to the presentinvention suggests a new concept in the etching process, namely“chemical-mechanical etching method” which have never been reported.

To describe the method for manufacturing barrier ribs according to thepresent invention in more detail, the method preferably includes thefollowing processes.

(1) a slurry is made by mixing glass powder and ceramic powder so that amixing ratio is in the range between 50:50 and 95:5(volume ratio), andthen mixing 20 to 40 wt % of solvent, 2 to 12 wt % of binder includingwater soluble components and solvent soluble components, 3 to 18 wt % ofplasticizer and 0.5 to 2 wt % of dispersion agent and defoaming agent onthe basis of 100 wt % of the mixed powder;

(2) a thick film is made by coating the slurry on the glass or metallower plate in the thickness of 5 to 200 μm, and then drying the coatedslurry naturally or artificially under a predetermined temperatureprofile condition;

(3) the etching protective pattern film partially soluble or insolubleto the etching solution is formed through printing or exposure,development and printing on the thick film formed on the glass or metalsubstrate;

(4) the thick film on which the protective pattern film is formed isetched into a barrier rib shape by water-spraying the solution or themixed solution in which the ceramic powder is included as etchingaccelerator; and

(5) the protective pattern film is removed and then the specimen issintered at 450° C. to 600° C. for 0.5 to 1 hour to manufacture thebarrier ribs for PDP.

In some cases, in the step (2), it is possible to make the green tape bycoating the slurry on a polymer carrier film in the thickness of 5 to200 μm and then drying the coated slurry naturally or artificially undera predetermined temperature profile condition; and then make the thickfilm for barrier rib by laminating the green tape, formed on the polymercarrier film, on the glass or metal substrate.

Thus, the terms used in this specification and claims “green tape” and“thick film” are used with the same concept when the slurry is directlyapplied to the glass or metal substrate used as a substrate of PDP.Though the terms have different meanings when the slurry is moved to theglass or metal substrate after being applied on a polymer carrier film,it should be understood that each of the terms does not have differentmeanings but designate a substantially identical object.

In addition, an amount of each component of the composition defined inthis specification is in the range which is generally receivable in theart related to the composition for forming barrier ribs of PDP. Withoutany special explanation, the range shows a minimum value and a maximumvalue suitable for the barrier rib forming composition. In the samereason, set conditions such as thickness of the barrier rib, reactiontemperature and reaction time in the manufacturing method are alsodefined in the range which is receivable for optimized practice.

The slurry making process of the step (1) mixes the components by usingthe well-known ball mill. In order to optimize the functions of theadded components, the slurry making process is conducted by two mixingstages.

At first, glass powder and ceramic powder is put into a ball millcontainer (or, PP film-Nalgen bottle) as much as much as 20 to 30% ofthe volume of the PP film-Nalgen bottle, and then 20 to 40 wt % ofsolvent is added on the basis of 100 wt % of the mixed powder. And then,dispersion agent and lubricant of the above-mentioned amount are addedthereto, and then ball-milled. The milling is executed for 1 to 24 hoursdepending on the agglomeration level of the powder, preferably 6 to 12hours as a first milling.

If the first milling is completed, binder and plasticizer of theabove-mentioned amount are added thereto, and the ball-milled again as asecond milling. The second milling is also executed for 1 to 48 hours,preferably 12 to 24 hours.

As for the coating process of the step (2), the slurry is coated on acarrier film such as a miler film or the rear plated glass substrate forPDP by using the doctor blade tape casting as shown in FIG. 3. For thecoating process, it is possible to use the die casting, the commacasting, the screen printing and so on in addition to the doctor bladetape casting, and also the die coating and the roll coating are alsopossible. As described above, the slurry may be shaped on a separatepolymer film substrate and then bonded thereon by pressing orlamination.

In the step (3), the etching protective pattern formed on the thick filmis printed in a barrier rib pattern by using a solvent soluble paste,which has very low solubility to the solution used as an etching liquid,or by laminating DFR (Dry Film photoResist) on the thick film and thepassing through exposure, development and printing. This protectivepattern is make of material not dissolved in the solution and havingmechanical strength to some extent to give strong resistance against thespraying pressure of the solution or the abrasive action of the ceramicparticles added to the mixed solution. The solvent soluble paste mayadopt an existing paste for forming barrier ribs. Particularly, the pastfor black matrix used for improving contrast of PDP may be used in theprinting. This printing advantageously gives high productivity andrequires low manufacture costs but disadvantageously shows low accuracyof patterns. Thus, in order to manufacture the fine pitch barrier ribs,DFR used for the sand blasting protective pattern film is preferablyused. This protective pattern film may be formed in the same way as themethod for forming the sand blasting protective pattern film.

In the step (4), solution or mixed solution including ceramic powder asetching accelerator is sprayed on the thick film on which the protectivepattern film is formed in order to etch the thick film in a barrier ribshape. In this step, the water soluble components in the binder aredissolved in the etching liquid, which is solution, thereby formingporous structure. In addition, the thick film having the porousstructure is removed by using mechanical energy of the sprayed solutionor mixed solution. As explained above, since using the chemical etchingfor dissolving the water soluble components of the binder into thesolution together with the mechanical etching using mechanical energy ofthe sprayed solution, it is possible to make the barrier ribs having ahigh width-length ratio and an excellent etched shape.

In order to improve the chemical etching speed of the thick film by thesolution, surfactant and wetting agent may be preferably added to thesolution.

The surfactant is not limited to any special example, but may bepreferably selected from alkyl benzene, Di-iso butyl ketone, dipentene,methoxy propyl acetate, xylenes, butyl glycol, cyclohexanol and so on.The wetting agent is not limited to any specific example, but may beselected from tri-methoxy silane, 3-aminopropyl trimethoxy silane,3-glycidoxypropyl trimethoxy silane and so on. Each of the surfactantand the wetting agent may adopt one compound among the above examples ora mixture having at least two compounds among them. An added amount ofthe surfactant is 0.5 to 10 wt % on the basis of the water which issolvent. An added amount of the wetting agent is 0.5 to 10 wt % on thebasis of the water which is solvent.

In order to increase the mechanical etching speed of the thick film bythe solution, ceramic powder of such as alumina, zirxonia, siliconcarbide and silicon nitride may be added. The added ceramic powder hasan average particle size in the range of 0.1 to 10 μm, and preferablyhas an angled shape to improve the etching efficiency. An added amountof the ceramic powder is preferably in the range of 0 to 30% on thebasis of volume of the water.

The etching speed of the thick film by the solution is affected by manyfactors such as solution temperature, pressure, flow rate, sprayingangle of the solution, shape of the spraying nozzle and scanning speed.Among these factors, the effect of the solution pressure on the etchingspeed is illustrated in FIG. 5 As shown in FIG. 5, the etching speed ofthe solution is substantially linearly increased according to thespraying pressure of the solution. On the while, the flow rate of thesolution increases the etching speed of the thick film in the way ofexponential function, as shown in FIG. 6. To obtain a suitable barrierrib shape, it is required to adjust these factors appropriately.

The present invention also proposes composition for forming barrier ribswhich may be used in the above-mentioned manufacturing method.

The composition for forming barrier ribs according to the presentinvention includes the following components.

(a) 100 wt % of mixture of glass powder and ceramic powder of which avolume ratio is in the range of 50:50 to 95:5;

(b) 20 to 40 wt % of solvent;

(c) 2 to 12 wt % of binder including water soluble components andsolvent soluble components together;

(d) 3 to 18 wt % of plasticizer; and

(e) 0.5 to 2 wt % of dispersion agent and/or defoaming agent.

This composition is coated on the rear plate of PDP or laminated thereonin a green tape shape to form a thick film having a thickness of 5 to200 μm. And then, after a protective pattern film for etching is formedon the thick film, the thick film is etched into a barrier rib shapehaving a height in the range of 100 to 200 μm by the solution or themixed solution which is an etching liquid.

The glass powder is a main component for forming the barrier ribs byplasticity, and has an average particle size of 0.1 to 10 μm. Asrepresentative examples, the glass powder may adopt PbO—B₂O₃—SiO₂,P₂O₅—B₂O₃—SiO₂ and Bi₂O₃—B₂O₃—SiO₂ or their mixtures.

The ceramic powder is a filling component which is sintered togetherwith the glass for improving strength and hardness of the barrier ribs.The ceramic powder may adopt Al₂O₃, fused silica, TiO₂ and ZnO₂, ortheir mixture, which has an average particle size of 1 to 10 μm.

The solvent is a component playing a role of dissolving organicadditives such as organic binder and plasticizer in order to givesuitable viscosity to the tape casting. The solvent preferably has lowboiling point and low viscosity. As representative examples, methylethyl ketone (MEK), ethyl alcohol, isopropyl alcohol, toluene, xylene.tri-chloro ethylene, butanol, methanol, acetone, cyclohexanol,nitro-propane, propanol, N-propanol and water may be used alone or inmixed state.

The binder has significantly different feature to the composition of thegenerally used thick film. A binder in the thick film is generally usedas a component acting as a film forming agent so that the film hassuitable strength after the slurry is dried. However, the binder used inthe present invention should be dissolved at a suitable speed into thesolution which is an etching liquid and keep strength so that thebarrier ribs may maintain their shape during the etching process, inaddition to the traditional role. In order to be etched by the solution,the binder should have water soluble components, namely water solublebinder characteristic.

However, since most of water soluble binders are rapidly absorbed in thewater, their strength is abruptly lowered when the water soluble binderscome in contact with the solution during the etching process, therebycausing collapse of the etched portion. As a result, it is very hard tosatisfy these requirements by using a binder having only onecharacteristic. Thus, in the present invention, two or more bindersincluding water soluble components and solvent soluble components aremixed.

As for the water soluble binder, one of polyvinyl alcohol (PVA),hydroxyethyl cellulose (HEC), polyvinyl acetate (PVAc), polyvinylpyrrolidine (PVP), methyl cellulose (MC), hydroxypropylmethyl cellulose(HPMC), polypropylene carbonate, waxes, emulsion and latex, or theirmixture may be used. The water soluble binder preferably has an averagemolecular weight of 5,000 to 300,000.

As for the solvent soluble binder, one of cellulose, ethyl cellulose(EC), polyvinyl butyral (PVB), polymethyl methacrylate (PMMA),polyacrylate ester, polyvinyl pyrrolidine (PVP), polyvinyl chloride,polyethylene, polytetraflouroethylene (PTFE), poly-α -methyl styrene,polyisobutylene, polyurethane, nitro-cellulose and methyl methacrylate,or their mixture may be used. The solvent soluble binder preferably hasan average molecular weight of 5,000 to 300,000.

An added amount of the binder is in the range of 2 to 12 wt % on thebasis of 100 wt % of the mixed powder, more preferably in the range of 3to 8 wt %. The binder preferably uses a mixture of the water solublebinder and the solvent soluble binder as described above. A mixed ratioof the water soluble binder and the solvent soluble binder is in therange of 20:1 to 1:20 on the basis of volume, preferably in the range of10:1 to 1:10.

In some cases, it is also possible to use only the water soluble binderand then etch a thick film containing the water soluble binder bysolution after semi-cross-linking the thick film so that the thick filmhas tolerance to some degree. However, a finally-obtained barrier ribshape of this thick film is more deteriorative than the case of usingboth water soluble binder and solvent soluble binder. Particularly,since the thick film containing only the water soluble binder requires aseparate semi-cross-linking process, the manufacturing procedure ofbarrier ribs is lengthened and the manufacture costs increase.

The plasticizer is a component which affects on the glass transitiontemperature and thus acts for controlling thermoplasticity. Asrepresentative examples, the plasticizer may adopt diethyl oxalate,polyethylene, polyethylene glycol (PEG), dimethyl phthalate (DMP),dibutyl phthalate (DBP), dioctyl phthalate (DOP), butyl benzylphthalate, polyalkylene glycols, polypropylene glycol (PPG),tri-ethylene glycol, propylene carbonate, water and butyl stearate, ortheir mixture.

For example, in case cellulose polymer is used as the binder, diethyloxalate is preferably used as the plasticizer. In addition, in case PVBor PMMA polymer is used as the binder, it is particularly preferred thatthe plasticizer adopts PEG, DMP, DBP and DOP. Furthermore, in case thewater soluble binder is emulsion or latex, the plasticizer preferablyadopts waxes or oil, which is not reacted with the water soluble binder.

An added amount of the plasticizer is preferably in the range of 3 to 18wt % on the basis of 100 wt % of the mixed powder, and more preferablyin the range of 6 to 10 wt %. The content of the additive changesdepending on the particle size of the mixed powder. In other words, asthe particle size of the powder is smaller, the added amount of theadditive increases.

The dispersion agent is a component acting for maintaining the glasspowder and the ceramic powder to be mutually dispersed in the slurry. Asrepresentative examples, one of menhaden fish oil, polyethyleneimine,glyceryl trioleate, polyacrylic acid, corn oil, polyisobutylene,linoleic acid, stearic acid, ammonium salt, salt acrylic acid, salt ofpoly acrylic acids, salt of methacrylic acids, linseed oil, glyceroltriolate, sodium silicate, dibutylamine, ethoxylate, phosphate ester and4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron), or their mixture maybe used for the dispersion agent.

The defoaming agent plays a role of changing the surface characteristicof the glass powder and the ceramic powder and reducing the interfacialtension of the solvent to remove foams. Stabilization of foams may begenerally controlled by static electricity characteristic out ofparticles in the aqueous solvent system. The defoaming agent isidentical to the dispersion agent in most cases, so compounds related tothe defoaming agent are not described in detail.

Organic matters in the composition of the present invention are resolvedbelow the plasticizing temperature of the barrier ribs, and thus do notaffect on the sintering density with giving an appropriate viscosityrange during the tape casting, thereby giving suitable viscosity in thethickness range, namely 5 to 200 μm, of the green tape required formaking the rear plate of DP.

In addition to the essential components, other components forreinforcing the barrier ribs and contributing to the convenience ofprocess may be added to the composition of the present invention if theydo not deteriorate the properties of the composition. In addition, otheradditional processes may be used without damaging the intension of thepresent invention.

The present invention also provides PDP (Plasma Display Panel)manufactured by using the rear plate on which the above-mentionedbarrier ribs are formed. The method for making PDP by using the rearplate on which the above-mentioned barrier ribs is well known in theart, and not described in detail.

Now, more concrete examples of the present invention are described withreference to the above-described embodiments, but the scope of theinvention is not limited to the following examples of course.

EMBODIMENT 1

100 g of powder including glass powder and alumina powder in the ratioof 8:2 is well mixed and then ball-milled for 25 hours. To this powdermixture, 23 g of water as solvent, 0.75 g of ammonium salt poly acrylicacid as dispersion agent, 9 g of hydroxy ethyl cellulose (HEC) and 0.3 gof acrylic emulsion as binder, polyethylene glycol (PEG) as plasticizer,0.3 g of BYD-024 (manufactured by BYK-Chemie Co.) as defoaming agent,and 0.3 g of BYK-346 (manufactured by BYK-Chemie Co.) as surfacecontroller are additionally mixed and then ball-milled again for 24hours to make composition for manufacturing barrier ribs of the PDPlower plate.

The composition slurry made in this way is coated on a miler film in thethickness of 180 μm by using the doctor blade tape casting, and thendried at 25° C. for 24 hours to make a green tape.

The obtained green tape is laminated by pressuring a glass substrate onwhich a back dielectric and an electrode are printed, in order to make athick film for manufacturing barrier ribs. And then, an etchingprotective film having a stripe pattern is printed on the thick film ina thickness of 40 μm, a width of 100 μm and a pitch of 420 μm by using ascreen printing device. This protective film is coated by using theblack paste (Okuno, Japan) for the sand blasting which is a non-aqueouspaste basically having no solubility to water.

Then, water is sprayed through nozzles at a pressure of 5 kgf and a flowrate of 1 ml/sec for about 8 minutes onto the thick film on which thepattern protective film in order to etch the thick film into a barrierrib shape. And then, the thick film is sintered at 570° C. for 30minutes to make the barrier ribs.

The barrier ribs are then observed by using a scanning electronmicroscope in order to check that a desired barrier rib is formed on thethick film on the glass substrate. As a result of the observation, it isfound that the barrier ribs are formed to have an average height of 127μm and an average thickness of 80 μm, as shown in FIG. 7.

EMBODIMENT 2

Barrier ribs are manufactured in the same way as the first embodiment,except that the composition for manufacturing barrier ribs containscomponents as seen in the following Table 1. TABLE 1 Compound Content(g) Solvent N-propanol/methanol 18 (mixture in a ratio of 1:1)Dispersion agent BYK-110 2 Water soluble binder polyvinyl pyrrolidine 9Solvent soluble binder methyl methacrylate 0.3 Plasticizer polyethyleneglycol 6 Defoaming agent BYK-024 0.3 Dispersion agent BYK-346 0.3

The barrier ribs are then observed by using a scanning electronmicroscope in order to check that a desired barrier rib is formed on thethick film on the glass substrate. As a result of the observation, it isfound that the barrier ribs are formed to have an average height of 140μm and an average thickness of 80 μm, as shown in FIG. 8.

COMPARATIVE EXAMPLE 1

Barrier ribs are formed by using composition including components assuggested in the following Table 2 through the same way as the firstembodiment. This comparative example 1 is different from the firstembodiment just in the point that polyvinyl alcohol which is watersoluble binder is uniquely used as the binder.

As a result of checking the shape of the obtained barrier ribs through ascanning electron microscope, it is found that many barriers are broken.TABLE 2 Compound Content (g) Solvent Water 17.5 Dispersion agent4,5-dihydroxy-1,3-benzenedisulfonic 2 acid: Tiron Binder polyvinylalcohol 9 Plasticizer polyethylene glycol 6 Defoaming agent BYK-024 0.3Dispersion agent BYK-346 0.3

COMPARATIVE EXAMPLE 2

Barrier ribs are manufactured in the same way as the first comparativeexample, except that the thick film is hardened at 150° C. for 45minutes in order to give tolerance against the solution (water) duringthe etching process, and then checked by a scanning electron microscope.

Different to the first comparative example, the barrier ribs of thesecond comparative example seldom have broken shapes, but does notmaintain a perfect shape as much as the case of the first and secondembodiments. In addition, because of using the separatesemi-cross-linking process before etching, the manufacturing procedureis lengthened and therefore the manufacturing costs are increased.

Various changes and modifications within the spirit and scope of theinvention will become apparent to those skilled in the art from thisdetailed description.

Industrial Applicability

As described above, by the method of manufacturing barrier ribs for DPDand the composition for the method according to the present invention,it is possible to prevent conventional problems such as dust generationcaused by the sand blasting and mechanical damage of barrier ribs sincethe thick film for forming the barrier ribs is etched with the use ofwater-based solution. In other words, it is possible to preventenvironmental pollution, which may be generated during forming thebarrier rib, by providing a pollution-free mechanical-chemical etching.In addition, since the mechanical etching and the chemical etching areapplied together, it is possible to manufacture the fine pitch barrierribs having a high width-length ratio, particularly barrier ribs havingcomplex shapes such as a meander type. In case of forming the barrierrib forming thick film by laminating the green tape on the substrate, itis possible to improve productivity of the thick film for the barrierribs and make the thick film quality uniform. As a result, themanufacturing method and the composition of the present invention mayimprove product reliability of the lower plate of PDP, production yieldand quality uniformity, and the barrier rib shaping process used in themethod may dramatically reduce the manufacture costs of the lower plateof PDP.

1. A method of manufacturing lower plate barrier ribs for a PlasmaDisplay Panel (PDP) comprising the steps of: forming a thick film (or,“green tape”) for barrier ribs on a glass or metal substrate by usingcomposition for forming the barrier ribs, which contains water solublecomponents and solvent soluble components together as a binder; forminga protective pattern film partially soluble or insoluble to the watersoluble solution on the thick film; etching the thick film into abarrier rib shape by using solution or mixed solution containing ceramicpowder as an etching accelerator; and sintering the etched thick film.2. A method of manufacturing lower plate barrier ribs for PDP accordingto claim 1, wherein the method comprises the steps of: (1) making aslurry by mixing glass powder and ceramic powder so that a mixing ratiois in the range between 50:50 and 95:5(volume ratio), and then mixing 20to 40 wt % of solvent, 2 to 12 wt % of binder including water solublecomponents and solvent soluble components, 3 to 18 wt % of plasticizerand 0.5 to 2 wt % of dispersion agent and defoaming agent on the basisof 100 wt % of the mixed powder; (2) making a thick film by coating theslurry of the glass or metal rear plate in the thickness of 5 to 200 μm,and then drying the coated slurry naturally or artificially under apredetermined temperature profile condition; (3) forming the etchingprotective pattern film partially soluble or insoluble to the solutionthrough printing or exposure, development and printing on the thick filmformed on the glass or metal substrate; (4) etching the thick film onwhich the protective pattern film is formed into a barrier rib shape bywater-spraying the solution or the mixed solution in which the ceramicpowder is included as etching accelerator; and (5) removing theprotective pattern film and then sintering the specimen at 450° C. to600° C. for 0.5 to 1 hour.
 3. A method of manufacturing lower platebarrier ribs for PDP according to claim 2, wherein the step (2) isexecuted by: making the green tape by coating the slurry on a polymercarrier film in the thickness of 5 to 200 μm and then drying the coatedslurry naturally or artificially under a predetermined temperatureprofile condition; and making the thick film for barrier rib bylaminating the green tape, formed on the polymer carrier film, on theglass or metal substrate.
 4. A method of manufacturing rear platebarrier ribs for PDP according to claim 1, wherein 0.5 to 10 wt % ofsurfactant and/or 0.5 to 10 wt % of wetting agent is added to thesolution on the basis of water, which is solvent.
 5. A method ofmanufacturing rear plate barrier ribs for PDP according to claim 1,wherein the ceramic powder added to the mixed solution has an angledshape and an average particle size of 0.1 to 10 μm, and an added amountof the ceramic powder is 0 to 30 wt % on the basis of water, which issolvent.
 6. Composition for manufacturing barrier ribs for a PlasmaDisplay Panel (PDP) comprising: (a) 100 wt % of mixture of glass powderand ceramic powder of which a volume ratio is in the range of 50:50 to95:5; (b) 20 to 40 wt % of solvent; (c) 2 to 12 wt % of binder includingwater soluble components and solvent soluble components together; (d) 3to 18 wt % of plasticizer; and (e) 0.5 to 2 wt % of dispersion agentand/or defoaming agent.
 7. Composition for manufacturing barrier ribsfor PDP according to claim 6, wherein the glass powder has an averageparticle size of 0.1 to 10 μm and is selected from the group consistingof PbO—B₂O₃—SiO₂, P₂O₅—B₂O₃—SiO₂ and Bi₂O₃—B₂O₃—SiO₂ or their mixtures;wherein the ceramic powder has an average particle size of 1 to 10 μmand is selected from the group consisting of Al₂O₃, fused silica, TiO₂and ZnO₂, or their mixtures; wherein the solvent is one solution or atleast two mixed solution selected from the group consisting of methylethyl ketone (MEK), ethyl alcohol, isopropyl alcohol, toluene, xylene,tri-chloro ethylene, butanol, methanol, acetone, cyclohexanol,nitro-propane, propanol, N-propanol and water; wherein the binder is amixture of water soluble binder and solvent soluble binder having avolume ratio in the range of 20:1 to 1:20; wherein the plasticizer isselected from the group consisting of diethyl oxalate, polyethylene,polyethylene glycol (PEG), dimethyl phthalate (DMP), dibutyl phthalate(DBP), diocyly phthalate (DOP), butyl benzyl phthalate, polyalkyleneglycols, polypropylene glycol (PPG), tri-ethylene glycol, propylenecarbonate, water and butyl stearate, or their mixture; and wherein thedispersion agent is selected from the group consisting of menhaden fishoil, polyethyleneimine, glyceryl trioleate, polyacrylic acid, corn oil,polyisobutylene, linoleic acid, stearic acid, ammonium salt, saltacrylic acid, salt of poly acrylic acids, salt of methacrylic acids,linseed oil, glycerol triolate, sodium silicate, dibutylamine,ethoxylate, phosphate ester and 4,5-dihydroxy-1,3-benzenedisulfonic acid(Tiron).
 8. Composition for manufacturing rear plate barrier ribs forPDP according to claim 7, wherein the water soluble binder is selectedfrom the group consisting of polyvinyl alcohol (PVA), hydroxyethylcellulose (HEC), polyvinyl acetate (PVAc), polyvinyl pyrrolidine (PVP),methyl cellulose (MC), Hdroxypropylmethyl cellulose (HPMC),polypropylene carbonate, waxes, emulsion and latex, or their mixture,and has an average molecular weight of 5,000 to 300,000; and wherein thesolvent soluble binder is selected from the group consisting ofcellulose, ethyl cellulose (EC), polyvinyl butyral (PVB), polymethylmethacrylate (PMMA), polyacrylate ester, polyvinyl pyrrolidine (PVP),polyvinyl chloride, polyethylene, polytetraflouroethylene (PTFE), poly-α-methyl styrene, polyisobutylene, polyurthane, nitro-cellulose andmethyl methacrylate, or their mixture, and has an average molecularweight of 5,000 to 300,000.
 9. A Plasma Display Panel (PDP) using thebarrier ribs manufactured according to the method defined in the claim1.